With wattles that size they are going to be much smaller come spring. There is no way to prevent frostbite on the wattles if you get as cold as you say. The wattles dip into the waterer, freeze, and then... Well, they wither up and fall off, usually with no intervention on your part. They may bleed onto the favorite hen's neck and back during mating, but that is the extent of the damage.
My roo had a glorious comb and wattles. He got a bad case of frostbite that resulted in him losing most of his wattles due to the waterer freezing them. He was absolutely fine except for the bleeding on his favorite girls. (I nearly had a heart attack seeing blood all over the girls' necks and backs. I searched and searched for wounds on them thinking they were bleeding. Some fellow BYCers helped to spot that the blood was from the roo, and not from the girls.)
Frostbite can be prevented as Imp said by keeping the coop dry and vented (but draft free), but do not beat yourself up too much if he gets it anyway because it happens sometimes. Vaseline and Bag Balm are good at preventing it from taking hold and doing damage.
Good luck.